set::equal_range

项目
03/27/2013

返回迭代器对分别到中的第一个元素设置为大于或等于指定的键的键以及在的第一个元素设置使用比键大的密钥。

pair <const_iterator, const_iterator> equal_range (
   const Key& _Key
) const;
pair <iterator, iterator> equal_range (
   const Key& _Key
);

参数

_Key
参数键与一个元素的排序关键字进行比较从一组搜索的。

返回值

第一个是 lower_bound 键和第二个迭代器对是键的 upper_bound。

为对第一个迭代 pr 跟成员函数返回的访问，请使用 pr。first和取消引用下限迭代器，使用* (pr。first)。为对第二个迭代 pr 跟成员函数返回的访问，请使用 pr。second和取消引用上限迭代器，使用* (pr。second)。

示例

// set_equal_range.cpp
// compile with: /EHsc
#include <set>
#include <iostream>

int main( )
{
   using namespace std;
   typedef set<int, less< int > > IntSet;
   IntSet s1;
   set <int, less< int > > :: const_iterator s1_RcIter;
   
   s1.insert( 10 );
   s1.insert( 20 );
   s1.insert( 30 );

   pair <IntSet::const_iterator, IntSet::const_iterator> p1, p2;
   p1 = s1.equal_range( 20 );

   cout << "The upper bound of the element with "
        << "a key of 20 in the set s1 is: "
        << *(p1.second) << "." << endl;

   cout << "The lower bound of the element with "
        << "a key of 20 in the set s1 is: "
        << *(p1.first) << "." << endl;

   // Compare the upper_bound called directly 
   s1_RcIter = s1.upper_bound( 20 );
   cout << "A direct call of upper_bound( 20 ) gives "
        << *s1_RcIter << "," << endl
        << "matching the 2nd element of the pair"
        << " returned by equal_range( 20 )." << endl;

   p2 = s1.equal_range( 40 );

   // If no match is found for the key,
   // both elements of the pair return end( )
   if ( ( p2.first == s1.end( ) ) && ( p2.second == s1.end( ) ) )
      cout << "The set s1 doesn't have an element "
           << "with a key less than 40." << endl;
   else
      cout << "The element of set s1 with a key >= 40 is: "
           << *(p1.first) << "." << endl;
}